Each of the following statements regarding vascular rings is true EXCEPT:

A. It is important to define the anatomy of a vascular ring by preoperative angiography. 
B. Left aortic arch with aberrant right subclavian artery may result in compression of the esophagus but does not result in a true complete vascular ring. 
C. The ligamentum arteriosum plays no role in the vascular ring created by a double aortic arch. 
D. Right aortic arch with left ligamentum arteriosum and retroesophageal left subclavian artery comprises a vascular ring that is treated by division of the ligamentum arteriosum. 
E. Right aortic arch with retroesophageal left subclavian artery is the most common form of right aortic arch anomaly.

Answer E

The term vascular ring refers to a constellation of developmental abnormalities of the aortic arch complex that result in compression of the trachea and/or esophagus. These anomalies can be classified into four groups: 1) double aortic arch, 2) right aortic arch with left ligamentum arteriosum, 3) left aortic arch and 4) pulmonary artery sling. The diagnosis of vascular ring is best made with a contrast study of the esophagus. Angiography is usually not performed unless a pulmonary artery sling is suspected.

In left aortic arch with retroesophageal subclavian artery there is compression of the esophagus between the subclavian artery posteriorly and the trachea anteriorly. While it is not a true complete ring, it is generally included in the discussion of vascular rings because of its anatomy and presentation. 

In the double aortic arch variant two arches arise from the ascending aorta; one passes on each side of the trachea and esophagus, and they recombine to form a single descending aorta. The airway and esophageal compression is produced by the two arches and does not involve the ligamentum arteriosum. 

The most common variant of right aortic arch with left ligamentum arteriosum involves a retroesophageal left subclavian artery. The ring is completed by the ligamentum arteriosum which extends from the descending aorta to the pulmonary artery. Division of the ligamentum releases the ring. 

The anomaly of pulmonary artery sling involves origination of the left pulmonary artery from the right pulmonary artery; the left pulmonary artery passes to the right of the trachea and between the trachea and esophagus. This results in compression of the lower trachea and is associated with abnormal distal tracheal development.